Two new weeds in Morocco: Ambrosia psilostachya ( Asteraceae ) and Datura ferox ( Solanaceae )

Tanji, A.: Two new weeds in Morocco: Ambrosia psilostachya ( Asteraceae ) and Datura ferox ( Solanaceae ). — Fl. Medit. 33: 225-232. 2023. — ISSN: 1120-4052 printed, 2240-4538 online. As a result of field surveys with special emphasis on weeds occurring in Moroccan farmlands, two recently introduced weed species ( Ambrosia psilostachya and Datura ferox ) have been found in several locations. A. psilostachya ( Asteraceae ) has been discovered in 2000 growing along roadsides. It is a perennial species that survives essentially through rhizomes and rootstocks, resulting in the establishment of clonal populations that form dense colonies on roadsides. It has been observed in March 2023 in 16 sites along national roads and highways. Datura ferox ( Solanaceae ) has been found in irrigated corn fields in 2022 and in a carrot field in 2023. Both species are unpalatable to livestock and will probably spread to other areas of Morocco. They are considered new naturalized weeds, which indicate that the country needs more botanical explorations. Herbariu specimens of both species were deposited at the national herbarium of the Institut Scientifique in Rabat.

I present here the distribution and status of two naturalized plant species in Morocco (Ambrosia psilostachya DC. and Datura ferox L.) that are expanding in the country.Photos, descriptions, and impacts of these newly introduced species are provided in the present note.
In Morocco, Western ragweed plants survive and expand primarily from horizontal and vertical rootstocks (Fig. 1).Since western ragweed is not palatable to livestock, some colonies prospered in sandy soils producing sometimes more than 100 stems m -2 and growing up to 1,40 m tall.Machines used for road construction and management certainly contributed a lot to rhizome dispersal.
From field observations, growth of new shoots occurs from November to April when minimal temperatures at night are 5 to 15 C, maximal temperatures in the day are 15 to 25 C, and the photoperiod is 10 to 12 hours.Stem growth and colony formation occur from January to May when minimal temperatures at night are 5 to 20 C, maximal temperatures in the day are 15 to 30 C, and the photoperiod is 10 to 13 hours.The flowering period is essentially from May to December.Panicles are predominantly formed with many male flowers at the top of the inflorescence, and only few female flowers at the base of the inflorescence.Seeds and seedlings have never been observed.Western ragweed is therefore considered, under local climatic conditions, a perennial weed in Morocco.
The dispersal strategy appears similar in all observed sites along roadsides and highways.In the first year, the individual plant does not appear to produce additional shoots from its root system.In the second year, new shoots emerge from the rootstocks, thus establishing a dense clone which can cover up to 1 or 2 m².Through its spreading rhizomes, a clamp can be formed or even an area can be colonized within few years.Dense colonies may rise questions about possible impact of western ragweed, through competition and allelopathy, on the local flora.

Chorology
Western ragweed is native of North and South America (Bassett & Crompton 1975; CABI 2023; POWO 2023).It is found in the 5 continents, and is usually distributed in roadsides, fields, and pastures (CABI 2023; POWO 2023; WFO 2023).In the Mediterranean region and surrounding areas, it was reported in Algeria, Italy,

Notes
Western ragweed is a perennial Asteraceae that survives primarily through rhizomes and rootstocks, resulting in the establishment of clonal populations that can cover rapidly  1975; Fried & al. 2015.It is an invasive weed in Australia (CABI 2023), in the USA (Vermeire & Gillen 2000), in France (Fried & al. 2015), in Iran (Saberi & al. 2022), and several other countries (GBIF 2023).It is considered one of the most common weeds in pastures and rangeland in the southern Great Plains region of the USA (Funderburg & al. 2014).It is an aggressive competitor with crops and is generally considered unpalatable to cattle (Vermeire & Gillen 2000).Leaf and rhizome extracts inhibited germination and early seedling growth in a range of Poaceae including wheat, oats and rye (Dalrymple & Rogers 1983).
Western ragweed is primarily anemophilous (wind-pollinated).It does shed large quantities of air-borne pollen that causes hay fever symptoms (Bassett & Crompton 1975).However, the pollen produced could potentially contribute to allergies by prolonging the presence of pollen in the air, and its effects on health might be aggravated by climate change (Wan & al. 2002; Fried & al. 2015).
Datura ferox belongs to the Solanaceae family that includes in Morocco 16 genera and 46 taxa, while the genus Datura contains 4 species: Datura inoxia Mill., D. metel L., D. stramonium L., and D. wrightii Regel (Fennane & al. 2007, Dobignard & Chatelain 2013, Pils 2022, efloramaghreb 2023, Peltier 2023).None of these references confirmed the presence of D. ferox in Morocco, and it is therefore considered an exotic weed species recently introduced into the country.
Fierce thornapple plants were found by the author in irrigated corn fields in Oualidia near the Atlantic Ocean (33°2′ 23" N, 8°41′ 30" W, altitude 10 m) and Khémis Mtouh (32°51′ 4" N, 8°8′ 55" W, altitude 160 m) in October 2020 (fall season) and in an irrigated carrot Table 1.Ambrosia psilostachya in 16 sites along national roads and highways from Settat to Sidi Slimane in Morocco in March 2023.field in Berrechid (33°17′ 41" N, 7°25′ 26" W, altitude 240 m) in May 2023 (early summer season).Pr.Ibn Tattou confirmed the identification of Datura ferox as a new exotic species in Morocco.Collected plants were at the flowering and fruiting stages (Fig. 2), and were growing in areas where daily temperatures in summer (June, July, August) usually exceed 30 C, nightly temperatures are around 20 C, and the photoperiod is 14 hours.D. ferox is therefore considered, under local climatic conditions, a summer annual weed in Morocco.

Chorology
Fierce thornapple is native to southern North America (CABI 2023; POWO 2023).It is located in roadsides, waste places, and cultivated lands.It is an annual plant that has become a significant weed of summer crops in many subtropical and warm temperate parts of the world.It is found in the 5 continents.In the Mediterranean region and surrounding areas, it was reported in the Canary Islands, Algeria, Israel, Greece, Italy, France, and Flora Mediterranea 33 -2023 229

Notes
Datura ferox is a noxious weed in warm and hot regions of the world where its control could be problematic.It is a competitive weed in Spain (San Martın & al. 2015), in Australia (Charles & al. 1998), in Argentina (Torres & al. 2013), in the United Arab Emirates (Shahid & Rao 2014), and several other countries (GBIF 2023).It is toxic to animals and humans, because all plant parts and seeds contain toxic alkaloids.Cases of livestock poisoning do occur, especially if animal feed is contaminated with D. ferox seeds (CABI 2023; POWO 2023).

Conclusion
Ambrosia coronopifolia and Datura ferox are new exotic weeds naturalized in Morocco.They are unpalatable to livestock and can be invasive in agricultural systems and uncropped areas.Both plant species were introduced into Morocco with human activities, which indicate that the country needs more thorough botanical explorations.

Fig. 2 .
Fig. 2. Datura ferox: a) general habit, b) leaves and flower, c) capsule, d) distribution in the map of Morocco.Photos by the author.